You can't stop her, but try to help her understand that although they are both sisters in the same household, they are different people at different points in their lives. She probably doesn't understand that her older sister wasn't allowed to do certain things until a certain age, and that she, too, will have to mature more to do those things. She must look up to her, so hopefully the older one realizes this and tries to help her understand also.

I went through this with my daughter and her older brother. I kept reminding her if she felt as if she was being a leader or a follower. They are both kids that like their freedom of expression and not fit into the norm. She had to face if she felt comfortable with herself by coping her brother.